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The paper reports an experimental study on the effect of compression ratio variation on the performance and pollutant emissions of a single-cylinder light-duty research diesel engine operating in DF mode. The architecture of the combustion system as well as the injection system represents the state-of-the-art of the automotive diesel technology. Two pistons with different bowl volume were selected for the experimental campaign, corresponding to two CR values: 16.5 and 14.5. The designs of the piston bowls were carefully performed with the 3D simulation in order to maintain the same air flow structure at the piston top dead center, thus keeping the same in-cylinder flow characteristics versus CR. The engine tests choice was performed to be representative of actual working conditions of an automotive light-duty diesel engine.

Research activities in the development of reliable computational models for aftertreatment systems are constantly increasing in the automotive field. These investigations are essential in order to get a complete understanding of the main catalytic processes which clearly have a great impact on tailpipe emissions. In this work, a 1D chemical reaction model to simulate the catalytic activity of a Pd/Rh Three-Way Catalyst (TWC) for a Natural Gas heavy-duty engine is presented. An extensive database of tests carried out with the use of a Synthetic Gas Bench (SGB) has been collected to investigate the methane abatement pathways, linked to the lambda variation and oxide formation on palladium surface. Specific steady-state tests have shown a dynamics of the methane conversion even at fixed λ and temperature conditions, essentially due to the Pd/PdO ratio.

The aim of this work has been to investigate the influence of bio-diesel (FAME - fatty acid methyl ester) and reasonable blends of FAME and diesel, on the behavior of the mixture formation, the combustion process and the emission levels of a modern diesel engine. Therefore experimental investigations have been carried out on a single cylinder engine which is a modification of a four cylinder production HSDI (high speed direct injection) diesel engine. Cylinder pressure and tail-pipe emissions have been measured. Additionally the injector has been mounted on a flow-metering device to gather information about the pure flow through the injection system depending on the fuel type. In parallel with the experimental investigations CFD (computational fluid dynamics) calculations have been carried out in order to closely check local effects inside the injector and the combustion chamber.

The present work is focused on multidimensional simulations of combustion in Diesel engines, using detailed kinetics reaction schemes. The selected reaction mechanism is the scheme developed by Liu et al. [1].The simulations are performed through the open source CFD Toolbox OpenFOAM (Open Field Operation and Manipulation). OpenFoam uses finite volume methods to solve systems of partial differential equations ascribed on any 3D unstructured mesh of polyhedral cells. A preliminary analysis relevant for diesel combustion studies is performed in constant volume homogeneous conditions. Here the treatment of the stiff ordinary differential equations arising from the usage of detailed kinetics reaction mechanisms and the performance of different solvers are investigated. The CVODE package has been integrated in OpenFOAM, as an alternative solver to the one provided by the original version of the code.

The EU emission standards for new rail Diesel engines are becoming even more stringent. EGR and SCR technologies can both be used to reduce NOx emissions; however, the use of EGR is usually accompanied by an increase in PM emissions and may require a DPF. On the other hand, the use of SCR requires on-board storage of urea. Thus, it is necessary to study these trade-offs in order to understand how these technologies can best be used in rail applications to meet new emission standards. The present study assesses the application of these technologies in Diesel railcars on a quantitative basis using one and three dimensional numerical simulation tools. In particular, the study considers a 560 kW railcar engine with the use of either EGR or SCR based solutions for NOx reduction. The NOx and PM emissions performances are evaluated over the C1 homologation cycle.

Active prechamber combustion systems for SI engines represent a feasible and effective solution in reducing fuel consumption and pollutant emissions for both marine and ground heavy-duty engines. However, reliable and low-cost numerical approaches need to be developed to support and speed-up their industrial design considering their geometry complexity and the involved multiple flow length scales. This work presents a CFD methodology based on the RANS approach for the simulation of active prechamber spark-ignition engines. To reduce the computational time, the gas exchange process is computed only in the prechamber region to correctly describe the flow and mixture distributions, while the whole cylinder geometry is considered only for the power-cycle (compression, combustion and expansion). Outside the prechamber the in-cylinder flow field at IVC is estimated from the measured swirl ratio.